1. Field of the Invention
The technical scope of the invention is that of safety and arming devices for projectiles, using micro-electromechanical technology.
2. Description of the Related Art
It is known to produce mechanical Safety and Arming Devices (SAD) that are incorporated into projectile fuses of any caliber. Today, these devices are sought to be made using MEMS (Micro Electro Mechanical Systems) technology enabling them to be considerably miniaturized making them able to be integrated into medium caliber projectiles, for example.
The purpose of safety and arming devices (SAD) is to isolate the detonator and explosive load of a projectile and to enable these two components of the pyrotechnic train to communicate only (according to present-day standards such as STANAG 4157) when at least two distinct firing environment conditions appear. The isolation between the detonator and the explosive load is more often than not made in the form of a plate, also called a screen, slider or barrier, which obstructs the slot by which these two components of the pyrotechnic train are made to communicate.
The firing environment conditions retained to allow the slide to be retracted are often as illustrated in EP-2077431 firstly the acceleration along the firing axis, and secondly, the spin acceleration of the projectile around its axis due to its spin-stabilization (firing from a rifled barrel).
Patent EP-2077431 uses these two loads in order, firstly, to release an inertial lock with a counterweight thanks to the acceleration along the firing axis then, secondly, to make the slider move transversally into a position in which it releases the slot thanks to the spin acceleration.
As it is presented in EP-2077431, the device suffers two drawbacks.
Firstly, the slider is hooked only to the inertial lock. The transversal stresses received by the slider further to impacts on the device (for example during the logistic phases or when the projectile is being rammed into position in the weapon) are thus communicated by the slider to the lock which risks being deviated and blocked and not being able to be released during firing.
Secondly, the lock's counterweight is subjected after unlocking to the transversal stresses due to the projectile's spin. These transversal stresses push the counterweight towards the slider and can cause it to unlock or even to be positioned in front of the slot, thereby disturbing priming.
By FR-2932561 a safety and arming device is also known that comprises a mobile screen immobilized by an inertial lock. The screen is armed by means of a gas generator. Such a device is not implemented in a projectile subjected to spin acceleration and the problem the invention is trying to overcome does not arise in this device. Note that the implementation of a gas generator to move the screen is a complicated and costly solution made necessary because of the absence of sufficient centrifugal inertia.